Eye Bars - Pins Connections

Abstract

This type of connections was used from the beginning of the steel constructions and is very efficient in some typical cases. Connections with eye bars and pins were used initially in suspension bridges, cantilever truss girders and other structures. In modern steel structures this type of connection is often used in cases when simple solutions are necessary like scaffoldings, mobile structures, emergency bridges, etc, or cases in which a certain rotation (pin connection) is desired like structures on cables, chimney, cable stayed bridges and bowstring bridges. At the end of the 19th century and the beginning of the 20th century, when the technology of foundation was not yet developed, engineers preferred the cantilever arrangement (known also as the Gerber system) to the continuous bridge, because it has favourable moments along its length and is not subjected to settlement stresses. It is important to mention that the cantilever truss girder is easier to analyse. However a cantilever arrangement requires special hinge connections and is less rigid than a continuous one. Some famous bridges have been built in this system. One of these structures of the past is the Traians bridge over the Mures in Arad, erected in 1910. The main cantilever truss has the following spans: L = 50,05 + 85,30 + 50,05 = 185,40 m. After two World Wars and other damages the bridge is still in operation for usual traffic - cars and tramways (with restrictions for trucks). The bridge is a historical monument of the engineering science and has a remarkable aesthetic aspect and an emblematical importance for the city of Arad. One of the aspects of the rehabilitation project is the analysis of the Gerber hinge which consists of lug plates and bolts in order to assure the movement of the suspended central part of the structure. These elements have to support the reaction force from all the loads on the bridge and they have a complex stress distribution. Due to the different events, the increasing of the traffic and traffic loads, the existence of cracks in these plates is possible and probable. The paper includes also the evaluation of the technical state of the bridge, stress evaluation based on 3D analysis, assessment of the remaining fatigue life.